Hi,
You need to look at the "order status" of your orders.
When the payment is done, your payment gateway normally sends a payment notification request to the payment plugin you're using, it checks its validity and change the status of the order from "created" to "confirmed".
That way, you can easily know which ones are paid and which ones aren't.
It's also possible that orders don't get confirmed if your payment gateway doesn't send payment notifications, or if there is a problem for it to contact your website (if it is in maintenance, not public, behind an htaccess requiring authentication, etc). In that case, we've made a list of things to check (for PayPal but it's quite similar for other payment gateways):
www.hikashop.com/support/documentation/i...or.html#notification